1. Field of the Invention
The present invention relates to a focused ion beam system that processes a sample by using focused ion beam, and a sample processing method using the same.
2. Description of the Related Art
Hitherto, focused ion beam systems have been used for, for example, performing etching processing on a semiconductor device to acquire a cross-section thereof for observation or processing a sample into a flake to produce a sample piece for a transmission electron microscope (TEM), which will be called TEM sample. The TEM sample is produced by removing both sides of an original sample by ion beam etching processing into a flake having an exposed cross-section to be observed. The flake may be moved by a manipulator having a probe (or needle), for example, to a sample holder for TEM observation to perform TEM observation. In this case, the needle is brought closer to the flake, and ion beam deposition is used to fix both of them, and the needle is manipulated to bring the flake closer to the sample holder. Then, ion beam deposition is used to fix the flake to the sample holder.
Since these operations are normally performed within the field of view of the focused ion beam system, the manipulator has low degree of freedom in operations. Thus, the flake taken out from an original sample is fixed to the sample holder at the same attitude (or in the same direction) as that is taken out. For example, since a semiconductor device has a wiring layer above and a substrate at the bottom, a flake from the semiconductor device is fixed to a sample base with the wiring layer thereabove.
The flake sample of the semiconductor device may further undergo a final process. Since the efficiency of etching with an ion beam is different in accordance with the materials of a wiring part, an interlayer insulating layer and a substrate, for example, some upper structures of samples may influence on the etching on the lower parts. For example, the influence of the upper structure may be significant in observing near a gate oxide film of a MOS transistor or observing the bottom of a via.
Accordingly, a technology has been disclosed that includes a focused ion beam system having a rotating mechanism that rotates a probe about the center axis thereof and a tilting mechanism that tilts the probe in the vertical direction about the probe as the center axis (see JP-A-2007-108105, FIG. 6).
According to the technology, a flake sample is fixed to the probe and is taken out from the original sample. Then, the probe is rotated about the center axis to invert the top-to-bottom direction of the sample. However, the probe is attached to the top surface of a sample holder at some angles. Thus, when the probe is rotated, the top surface of the sample and the top surface of the sample holder are not parallel. The tilting mechanism is used to tilt the probe so that the top surface of the sample and the top surface of the sample holder can be parallel. Then, the sample is moved to the sample holder and is fixed thereto. In this way, the lower part of the semiconductor device is turned upward such that a final process can be performed including irradiating an argon ion beam, for example, and removing a damaged layer of the sample.
However, the method using the probe having the rotating mechanism and the tilting mechanism may require a tilt angle of several tens degrees in accordance with the attached angles of the probe, and the tilting mechanism may be required to have a large stroke. However, it is difficult to provide the tilting mechanism in a narrow space near a sample within the focused ion beam system, which may increase the costs.
The invention was made in order to solve the problems, and it is an object of the invention to provide a focused ion beam system including microtweezers and a rotating mechanism therefor as manipulators so that the direction of a sample can be changed and the sample can be fixed to a sample holder, without requiring a tilting mechanism, and a sample processing method using the same.